Amend the last local commit

git commit --amend replaces the latest commit on the current branch.

Before using it, inspect both the latest commit and the index:

git show --stat --oneline HEAD
git diff --staged

To change only the commit message, run:

git commit --amend

To include a correction, stage it first, then amend. The new commit uses the complete current index, not only the last file you staged.

git add README.md
git diff --staged
git commit --amend --no-edit

Amending creates a new commit with a new ID. The parent normally stays the same, but the message, snapshot, author metadata, or committer metadata can differ.

Use amend on local work. Avoid replacing a commit that other people may already have. Their history still contains the old ID, so a later push can require history rewriting and create unnecessary recovery work.

If the commit is already shared, make a normal follow-up commit instead. It is less elegant, but it preserves the common history.

Exercise: amend a disposable commit, then run git log --oneline -2. Explain why the replacement appears as one commit rather than an extra child.